This web page is designed to give feedback to volunteers that have taken part in a Blue Ventures expedition in Madagascar. Volunteers have been collecting data alongside our Expedition team in Madagascar since 2003 and shared below are the results of the ecological surveys they undertake while on expedition. For more information about the work that Blue Ventures and their volunteers do please visit our expedition page.

Our Surveys

Your expedition

Reef types

Fringing reefs are those that grow directly from a shore and are found at shallower depths (e.g. Near Shore Coco Beach, Near Shore Half Moon).

Barrier reefs occur further out to sea. They follow the shoreline but are separated from it by a deeper lagoon (e.g. Christmas Reef, Lost).

Finally patch reefs are smaller, more isolated areas of reef that are surrounded by sand (e.g. MAH, 007).

Reserves vs Fished

Reserve sites are reefs that lie within areas that have been designated as No Take Zones (NTZs) by the local community. In these NTZs no extractive activities (i.e. fishing) are allowed to take place.

For each reserve survey site a corresponding site which is fished has been chosen. This is a site which is similar in character to the reserve (the same reef type, similar location) but is still open to fishing. In this way any changes over time can be attributed to the environment in general (if occurring at both sites) or the NTZ (if only seen at the reserve).

The results

These surveys have contributed to our unrivalled data set which allows us to see change in reef health over the years since 2003.

The current year is not included in trends analysis, as data is not representative of all  sites surveyed and so cannot be reliably compared.


Volunteers count the number of each species of fish they see as they swim along a 20 m transect line. There are more than 150 different species of fish to learn and encounter. The number and types of fish at a site can tell us about overall reef health and how fishing is having an effect.

These results show that in general there are more individual fish and a greater number of fish species within reserve sites (as opposed to fished sites). This is also true for patch reefs. For example on patch reefs of the Agnorondriake reserve (007, THB and Recruitment), large shoals of fusiliers are a common sight and this will lead to a higher average number of fish recorded.

Benthic Cover

The benthos (what’s on the bottom) is an important indicator of reef health. Without the structure that hard coral provides, the rest of the creatures that live on the reef cannot survive. We measure benthic cover using a Point Intercept Transect (PIT). Volunteers record what is directly below a tape measure at every 10 cm interval.

Hard coral cover in Velondriake has been affected by several destructive cyclones and bleaching events which kill hard corals. Each time a destructive event occurs coral cover decreases and algae has space to grow. However, our results show the beginnings of recovery each time. As climate change leads to an increased frequency of these events we are watching closely to see what will happen in the future.


Volunteers record key invertebrate species along a 10 m x 2 m belt transect. These species include slow growing molluscs such as giant clams and triton shells. Crown of thorns starfish feed on corals and can have a devastating effect when they swarm in large numbers. Sea cucumbers are an important commercial species that is highly fished.

Results show that the biggest invertebrates such as triton trumpet shells are very rare, many have been fished and populations take a long time to recover. Crown of thorns starfish is also low in numbers which is good news for the reef. Sea cucumbers are generally declining in numbers – probably due to overfishing.

Thank you

Without your help Blue Ventures would not be able to feed this information back to communities to allow them to make important decisions about the management of their reefs.

We have also used this data to publish several scientific papers.

As well as conducting their own survey work, volunteers also buddy staff when carrying out more complex surveys (such as coral bleaching and fish biomass). Results from these surveys are coming soon!

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